additional source Rowe, F.W.E., A.N. Baker, & H.E.S. Clark. (1988) The morphology, development and taxonomic status of Xyloplax Baker, Rowe and Clark (1986) (Echinodermata: Concentricycloidea), with the description of a new species. Proceedings of the Royal Society of London B 233: 431-459., available online athttp://dx.doi.org/10.1098/rspb.1988.0032[details]